How is kidney failure diagnosed?

Diagnosis of kidney failure is confirmed by blood tests measuring the buildup of waste products in the blood. BUN,creatinine, and GFR are routine blood tests used to measure the buildup of waste products in the blood. BUN and creatinine become elevated, and the glomerular filtration rate (GFR) decreases. This is the rate with which blood is filtered through the kidneys and can be calculated based upon the creatinine level, age, race, and gender.

Urine tests may be done to measure the amount of protein, detect the presence of abnormal cells, or measure the concentration of electrolytes. Protein in the urine is not normal and can be a clue that damage to the kidneys has occurred. When the urine is examined under a microscope, abnormal aggregations of red and white blood cells called casts can be seen in the urine with kidney disease. Comparing the concentrations of electrolytes in the blood and urine can help decide whether the kidneys are able to appropriately monitor and filter blood.

Other tests are used to diagnose the type of kidney failure. Abdominal ultrasound can assess the size of the kidneys and may identify whether any obstruction exists. Biopsy of the kidney uses a thin needle that is placed through the skin into the kidney itself to get bits of tissue to examine under the microscope.